Based on extensive electrostatic discharge (ESD) testing, common gate field effect transistors (FETs) have been identified as a weak point of a differential cascode amplifier circuit. Common source FETs of the differential cascode amplifier circuit have reverse diode chains that offer effective ESD protection. An output of the differential cascode amplifier circuit is provided by drains of the common gate FETs. In typical applications, the output nodes can operate at 24 VDC. Typical ESD protection, such as diode chains or clamps, are not viable options. Because of the high voltage, many series diodes are needed, which takes up too much area on a chip. Conventional ESD clamps have large parasitics and degrade radio frequency (RF) performance.
It would be desirable to implement an ESD protection circuit for cascode amplifiers that avoids the above problems.